Manual primer mechanism



March 7, 1967- D. N. ARNDT ETAL 3,307,836

MANUAL PRIMER MECHANI SM Filed Jan. 15, 1965 2 Sheets-Sheet l lNVENTORSDONALD N. ARNDT CHARLES H. TUCKEY BY J. D. TUCKEY ATTORNEYS D. N. ARNDTETAL 3,307,836

MANUAL PRIMER MECHANISM March 7, 1967 2 Sheets-Sheet 2 Filed Jan. 15,1965 FIG-2 FIG.3

INVEN TORS DONALD N. ARNDT CHARLES H. TUCKEY B) J. D. TUCKEY g M @imzzATTORNEYS United States Patent O 3,307,836 7 MANUAL PRIMERMECHANISMDonald N. Arnd t, Charles H. Tuckey and .I. D. Tuckey, Cass City, Mich,assignors to Walbro Corporation, Cass City, Mich, a corporation ofMichigan Filed Jan, 15, 1965, Ser. No. 425,715 1 Claim. (Cl. 261-34)This invention relates to a manual primer for carburetcm and is morespecifically directed to a primer for carburetors for small engines,such as are used on power lawn mowers, chain saws, go-ca rts and thelike.

Very frequently the starting of an engine is difficult particularly whenthe engine has been used to a conside'rable extent and the ignitionsystem is apt to be weaker than it is intended to be. difficult when anengine has been sitting for some time Without being used and gasolinehas evaporated from the passages of the carburetor so that it is notimmediately available to the engine manifold.

It is an object of the present invention to provide a relatively simplemanual primer which can introduce gasoline into the venturi throat ofthe carburetor Where it will become immediately available to the engine.Briefly, this is accomplished by a pressure device which can be utilizedin combination with the normal vent of the carburetor to the fuelchamber to apply momentary pressure to the surface of the fuel in thefuel reservoir forcing fuel into the carburetor jet.

Other objects and features of the invention relating to details ofconstruction and operation will be apparent in the following descriptionand claim.

Drawings accompany the disclosure and the various views thereof may bebriefly described as:

FIGURE 1 is a sectional view of the carburetor showing the manual primerin relation to the other parts.

FIGURE 2 is a top view of the carburetor.

FIGURE 3 is a horizontal section through the carburetor.

Referring to the drawings:

A carburetor housing H has a fuel inlet 20 controlled by a needle valve22 actuated by a lift member 24 on a standard ring float 26 pivoted at28 in a carburetor bowl 30, the bowl being suitably sealed at 32 to thehousing. A spring-pressed drain pin 34 is provided at the bottom of thebowl and a brass nipple insert 36 screws into a depending portion 38 ofthe housing which serves as a mount post for the float chamber shell 30,there being suitable sealing washers 48 provided. In the threadedpassage above the nipple 36 is a main fuel jet stem having a threadedportion 41 and an upward extending portion 42 extending into thehorizontal venturi passage 44. In the nipple 36 is a threaded needlevalve 46 to control the central passage 50 of the jet 42.

Fuel reaches the jet through a short passage 52 in portion 38 of housingH leading from the flat chamber to the space between the nipple 36 andthe jet base 41. A suitable idling system can be provided throughpassage 54 shown in FIGURE 1 and a passage 56 shown in FIG- URE 3terminating in idle ports 58 and 60, the port 60 being controlled by asuitable needle valve 62, these ports being located adjacent thethrottle valve 64. In the inlet of the venturi passage 44 is a chokevalve 66 of standard construction.

The primer mechanism is mounted on a tube 7 which projects down throughthe housing H and through the venturi passage 44 into the top of thefloat bowl chamber as shown in FIGURE 1. The end opening 72 of the tube70 is positioned above the normal liquid level in the float bowl.Mounted on the tube 70 by a sleeve 74 is a small cup-like chamber 76having a round de- The starting is also pending projection 77 which isfirictionally engaged with the sleeve 74, the other end of the sleevebeing frictionally engaged with the top of tube 70. The cup 76 has aflange 78 and is capped by a cover 80 which is preferably of suchmaterial as a resilient plastic so that it may have a snap-onconnection.

Within the cup 76 is a plunger P formed of a disc 82 and a disc 84 whichlie on either side of the center of a resilient sealing member 86, thesides of which extend beyond the disc 84 to contact, in a slidablesealing relation, the cylindrical walls of the cup 76. A small button 88having an enlarged flange 90 at the bottom is captive within the cup andcover and is projected outwardly by (reason of the compression spring 92seated on the bottom of the cup 76 and located on a small projection 94on disc 82. This piston assembly can be made in various ways. Onepreferred embodiment comprises forming the button 88 as a unit andassembling the perforated sealing member 86 and perforated discs 82 and84 over the projection 94 in frictional engagement. A small opening 96in the wall of the cup normally vents the top of the float bowl chamberto atmosphere through the cup 76 and the tube 70.

In the operation of the manual primer, it will be seen that when thebutton 88 is pressed downwardly against the action of the spring 92, theatmospheric vent 96 will first be closed by the downward movement of theplunger P and then pressure will develop in the cup which is transmittedthrough tube 70 to the surface of the fuel in the float bowl. This willcause it to squirt into the passage 52 and up through the jet passage 50into the Venturi, thus providing an immediate supply of fuel for enginestarting. Repeated operation of the button will supplement this fuelinjection and the engine being supplied may be readily started with anample supply of fuel.

It will thus be seen that with a very simple mechanism to apply airpressure to the surface of the fuel in the float chamber, supplementalfuel may be supplied to the venturi passage of the carburetor.

We claim:

In a carubertor for furnishing fuel to the intake manifold of aninternal combustion engine and of the type having a fuel supply chamberconnected to a venturi passage, an improvement for introducingsupplemental fuel into said venturi passage comprising:

(a) a rigid tube mounted in said carburetor and projecting upwardlytherefrom, said tube having a connection to the top of a fuel supplychamber above the normal fuel level in said chamber,

(b) a cup mounted on and supported by said tube having a dependinghollow projection pneumatically associated with the interior of saidtube, said cup having a lipped upper edge,

(0) an apertured cap for said cup having a peripheral flange to snapover the lipped edge of said cup, and

(d) a piston in said cup retained therein by said cap and having abutton projection extending through said cap, said piston being biasedoutwardly wherein it may be reciprocated to create above atmosphericpressure in said tube.

References Cited by the Examiner UNITED STATES PATENTS 2,827,272 3/1958Phillips 261-41 FOREIGN PATENTS 594,982 9/1925 France. 598,578 12/1925France.

5,551 1/1916 Great Britain.

HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner.

